In total hip replacement, there are several designs which address different indications for hip replacement depending on the quality and geometry of the patient's bones. Hip implants generally replace the femoral head and the acetabular socket with the objectives of restoring stable pain-free motion. There are several different designs of femoral components. In some designs, just the surface of the femoral head is replaced, while other designs are composed of a stem and head-neck section.
With resurfacing designed femoral components, minimal bone is removed; however complications with implant loosening can occur due to the ability of the bone to support the implant. With the stemmed femoral components, the implant is fixed within the canal of the femur. The effectiveness of this design is dependent, at least in part, on the strength of the cancellous bone within the canal of the femur. Without proper strength, the stem can subside (sink) further into the canal creating instability and, in some cases, fractures. Both scenarios can result in undesirable revision surgery.